Convert an Object to JSON

This code has been declared by its author to be Public Domain code.

Convert an Object to JSON by N

2009

This does about what it says, using reflection. The only thing that doesn't really work too well is multidim arrays, because those are grade-A insanity to work with. Objects that have already been converted are referenced only by their handle (which is, to be perfectly honest, just the their memory address, but it works well enough) - no type name is provided for them, since they've already been mentioned at least once before the current object/field/what have you in the JSON.

To use it, you call ObjectToJSON(obj, map) where obj is the object you want to convert to JSON and map is a TMap you'll use to store which objects have already been converted to JSON. If objects have dependencies on one-another or reference each other, you should try to create one TMap for that group of objects so as to reduce the size of the JSON output.

SuperStrict

Private
Function _objtoptr:Byte Ptr(obj:Byte Ptr)
	Return obj
End Function
Global ObjToPtr:Byte Ptr(obj:Object)=Byte Ptr(_objtoptr)

Function FieldToJSON:String(fid:TField, forObject:Object, map:TMap)
	Select fid.TypeId()
		Case IntTypeId,ShortTypeId,ByteTypeId
			Return String(fid.GetInt(forObject))
		Case LongTypeId
			Return String(fid.GetLong(forObject))
		Case DoubleTypeId
			Return String(fid.GetDouble(forObject))
		Case FloatTypeId
			Return String(fid.GetFloat(forObject))
		Default
			Return ObjectToJSON(fid.Get(forObject), map)
	End Select
End Function

Public

' The map argument is used to record what objects have already been put in a prior part of any JSON string
Function ObjectToJSON:String(obj:Object, map:TMap)
	Assert map Else "Inspection map not present"
	
	Local name$ = Int(ObjToPtr(obj))
	Local result$
	
	Local tid:TTypeId = TTypeId.ForObject(obj)
	
	If tid = Null Then
		Return "null"
	EndIf
	
	If tid <> StringTypeId And tid._class <> ArrayTypeId._class And map.Contains(name) Then
		Return "{~qhandle~q: "+name+"}"
	EndIf
	
	map.Insert(name,name)
	
	If tid._class = ArrayTypeId._class Then
		If tid.Name().StartsWith("Null[") Then
			Return "null"
		EndIf
		
		result = "{~qhandle~q: "+name+", ~qtype~q: ~q"+tid.Name()+"~q"
		Local elemt:TTypeId = tid.ElementType()
		If elemt Then
			Local dimensions:Int = tid.ArrayDimensions(obj)
			result :+ ", dimensions: ["
			
			Local dimString$ = ""
			Local last:Int = 1
			For Local dim:Int = dimensions-1 To 0 Step -1
				Local dimLength:Int = tid.ArrayLength(obj, dim)
				
				If dim < dimensions-1 Then
					dimString = ", " + dimString
				EndIf
				
				dimString = (dimLength / last) + dimString
				last = dimLength
			Next
			result :+ dimString
			result :+ "]"
			
			Local elems:String[] = New String[tid.ArrayLength(obj, 0)]
			For Local i:Int = 0 Until elems.Length
				Select elemt
					Case IntTypeId, ShortTypeId, ByteTypeId, LongTypeId, DoubleTypeId, FloatTypeId
						elems[i] = String(tid.GetArrayElement(obj, i))
					Default
						elems[i] = ObjectToJSON(tid.GetArrayElement(obj, i), map)
				End Select
			Next
			
			result :+ ", ~qcontent~q: ["+(", ".Join(elems))+"]}"
		Else
			result :+ ", ~qcontent~q: []}"
		EndIf
	ElseIf tid = StringTypeId
		If String(obj) = Null Then
			Return "~q~q"
		EndIf
		result = "~q" + String(obj).Replace("~q", "\~q").Replace("~n", "\n").Replace("~t", "\t").Replace("~r", "\r").Replace("~0", "\0") + "~q"
	Else
		If Not obj Then
			Return "null"
		EndIf
		
		result = "{~qhandle~q: "+name+", ~qtype~q: ~q"+tid.Name()+"~q"
		
		Local fields:TList = tid.EnumFields()
		Local enum:TListEnum = fields.ObjectEnumerator()
		
		While enum.HasNext()
			Local fid:TField = TField(enum.NextObject())
			result :+ ", ~q."+fid.Name()+"~q: "+FieldToJSON(fid, obj, map)
		Wend
		
		result :+ "}"
	EndIf
	
	Return result
End Function

Comments

2009

Updated to have slightly better multidimensional array support. An array of integers called 'dimensions' will precede the 'content' field for storing array data. This contains the length of each array dimension (for some reason brl.Reflection's TTypeID#ArrayLength reports the length of a dimension in terms of every element accessible from a dimension onward, so this only includes the size of each dimension on its own).

Code Archives Forum